The present invention is generally related to effervescent products, and, more particularly, is related to effervescent products including perborate salts, and to a method for producing same.
One major limitation in effervescent cleaning, disinfecting, or other products was the amount and type of liquid and active ingredients that could be incorporated into effervescent formulations. Generally, less than 25% by weight of an effervescent formulation in the form of a tablet or effervescent granules was available for active ingredients. Typically, surfactants, e.g., anionic, nonionic, cationic and amphoteric surfactants, could be used at no more than 5% of the effervescent formulas because these ingredients reduced the storage stability of carbonate-based effervescent products, made conventional granulation or tableting difficult or impossible, and dramatically increased the dissolution time of the resulting products. If greater than 5% by weight surfactants was used, then it usually became necessary to use disintegrants to enable dissolution of the composition.
Generally, solvents were incompatible with effervescent products. They were either very hydrophobic and were incompatible with aqueous systems, or were sufficiently hydrophilic to initiate the effervescent reaction, thus making the product unstable. Many surfactants were available only as liquids containing water or alcohol and could not be employed at any useful level in effervescent formulas. Previously, solvents were primarily used in effervescent tablet production for wet granulation and were evaporated in order to produce a finished tablet.
As noted previously, in typical effervescent tablets, less than 25% by weight of the tablet was usually available for ingredients other than the effervescent system. For example, although up to 75% by weight of the tablet weight could be a binder, only about 10% to 25% was typically used. The effervescent system typically accounted for up to 50% of the tablet. It should be noted that the more of the effervescent system that was used, the quicker the tablet dissolved, but less of the tablet was available for other desired ingredients. Lubricants, which help in tablet production, comprised up to approximately 10% by weight of the conventional tablet. Fragrance and color made approximately 2% of the tablet. It was found in conventional tablets that higher levels of fragrance adversely affected tablet stability, dissolution, hardness and tablet production.
One solution has been to replace the typical carbonate-based system with anhydrous perborate salt. The use of sodium perborate anhydrous in non-aqueous liquid-built detergent compositions is disclosed in Great Britain Patent Number GB-A-No. 1,205,711 (the ""711 patent). The ""711 patent, though, gives no further details are given of what is exactly meant by sodium perborate, anhydrous, and does not address improved dispersibility of the detergent in the wash water by addition of sodium perborate anhydrous.
Anhydrous perborate has also been noted as a potential effervescent system, which upon contact with water provides oxygen gas. For example, U.S. Pat. No. 4,772,412 (the ""412 patent), issued to Green, et al., discloses a process for making an anhydrous perborate that can be used in non-aqueous liquid detergents.
Effervescent compounds have been developed that include anhydrous perborate salts for the purpose of improving the dispensing or dissolution of detergent compositions into the washing water or for improvement of the delivery of the detergent actives of the composition to the wash or for improved sudsing. See, for example, Patent Cooperation Treaty Application Number US99/10008, International Publication Number WO 99/58444 (the 10008 application) and Patent Cooperation Treaty Application Number US99/10007, International Publication Number WO 99/58632 (the 10007 application). However, the 10008 application provides that the anhydrous perborate salt be intimately mixed with a diluent, which could be a process that would add time and cost to the manufacture of the end product detergent. Further, the mixture of the anhydrous perborate salt and diluent is either dehydrated, or the solvent of the non-aqueous diluent is dried, further adding to the time and cost of producing the end product detergent. Additionally, depending on the conditions of the dehydration of the hydrated perborate salt, or the drying process of the diluent, certain amounts of hydrated perborate salt may be present in the product of the 10008 application, which limits the product to uses where bleaching action is acceptable.
In addition to the diluent that may be mixed with the anhydrous perborate salt, the 10007 Application provides that the anhydrous perborate salt be coated with a coating material in order to improve its stability. While this relieves the need for incorporation of high levels of perborate, monohydrate, it adds a further step to the production of the detergent compound, thereby increasing time and cost of the manufacture, as well as the weight and size of the end product detergent particles.
One conventional form of sodium perborate, anhydrous (oxoborate) is manufactured by and commercially available from Degussa-Hxc3xcills AG in Frankfurt, Germany. It can be produced as described in European Patent Number EU0053859, generally by application of heat to a hydrated perborate salt, and under vacuum so as to draw off immediately any vapor released upon the application of heat. The commercially available oxoborate effervesces, but is difficult to use in tablets without the addition of additives. See U.S. Pat. Nos. 4,409,118 and 4,857,224. When loaded with solvents or liquid ingredients, the oxoborate begins to clump when the solvents or liquid ingredients comprise about 60% of its weight. The oxoborate becomes a paste at higher levels of loading with solvents or liquid ingredients.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.
The present invention provides both an effervescent system and a carrier for liquid ingredients to be used in effervescent compounds and a method for making a carrier for liquid ingredients to be used in effervescent compounds. Briefly described, the carrier is an expanded perborate salt anhydrous (EPB) which is both an effervescent material and a carrier that can be loaded with up to 1.2 times its weight with a solvent or liquid ingredient in which may be dissolved many different materials. The EPB remains a free-flowing dry powder suitable for incorporation into effervescent tablets, granules or powders.
Further, the present invention can also be viewed as providing a method for producing the EPB. The method includes the steps of heating a perborate salt monohydrate at a temperature and for an amount of time to produce the expanded perborate salt, anhydrous.
The present invention can also be viewed as providing for effervescent compounds incorporating EPB, and a method for making the effervescent compounds. In this regard, the method can be broadly summarized by the following steps: providing a solvent or liquid ingredient; providing an effervescent system, including EPB, in powder form; and mixing the solvent or liquid ingredient with the effervescent system, thereby producing a free-flowing effervescent compound. Alternative embodiments of the present invention include the further steps of dissolving ingredient(s) in a solvent or liquid ingredient and mixing the resulting solution with the effervescent system thereby producing a free-flowing effervescent compound. Further, the method may include compressing the effervescent compound and forming granules of the effervescent compound. In an alternative embodiment, the method may also include compressing the effervescent compound and forming a tablet from the effervescent compound.
Other methods, features, and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the following detailed description and figure. It is intended that all such additional methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.